Cougar investigators find gearbox flaw from earlier alert

Investigators scouring the wreckage of the Cougar Helicopters S-92A that crashed or ditched off the coast of Newfoundland 12 March, killing 17 of 18 onboard, have discovered a broken main gearbox (MGB) component that was the subject of a 28 January alert from Sikorsky.

Alert Services Bulletin 92-63-014 called on operators to replace three titanium studs that hold the main gearbox oil filter bowl in place with steel studs within the next 1,250h or within one year, whichever occurred first.

In Canada, investigators have discovered a broken titanium stud in the crashed Cougar S-92A gearbox, a find that could explain the pilots' reports of MGB oil pressure loss before the aircraft reversed direction and headed back toward land on the flight to oil rigs off the coast Thursday morning.

Flight International has learned that during a similar incident with a broken stud in Australia in early February, pilots reported a main transmission oil pressure warning and decreasing oil pressure. The crew in that case performed a forced landing on land and no one was injured.

Given the Cougar find, it is expected that the US Federal Aviation Administration and others will issue a directive that will ground the twin-engine heavy helicopters until the studs are changed out.